Which type of turbine (Pelton, Kaplan, Francis, etc.) would be suitable and deliver the best efficiency when driven by a high velocity forced air jet of 125-200 mph through a nozzle of 2-2.5 inches diameter? The desired outcome is maximum torque in the 300-400 rpm range.

The turbine should preferably be enclosed.

  • $\begingroup$ Sounds like a turbocharger from a truck, except for the low RPM. Can you gear down a high-speed turbine? Also, why turbine specifically, rather than any other sort of pneumatic motor? $\endgroup$
    – Dave Tweed
    Oct 16 '15 at 12:05
  • $\begingroup$ Thanks Dave. But no, it isn't a turbocharger. It is a prototype of a portable farm implement that I am trying to build. $\endgroup$
    – Ganesh
    Oct 17 '15 at 3:20
  • $\begingroup$ I wasn't suggesting that it was. I was trying to hint that a truck turbocharger turbine is an existing device that is close to what you're asking for. Is there any reason that its design wouldn't be suitable for your application? $\endgroup$
    – Dave Tweed
    Oct 17 '15 at 3:23
  • $\begingroup$ Air pressure before the nozzle? $\endgroup$
    – mart
    Oct 19 '15 at 8:06

Pelton, Kaplan, and Francis turbines are designed for non-compressible fluids (aka water not air). While they will certainly spin, they would be very inefficient and not what you are after. You will want to use a pneumatic motor or exhaust turbine like Dave Tweed recommended in the comments. Read the last paragraph of the function section for reference: https://en.wikipedia.org/wiki/Pelton_wheel#Function

Pneumatic is generally not a good way to transfer power. Most farm implements use PTO mechanical rotation or hydraulic power. Hydraulics have many benefits over pneumatic; efficiency, noise, power to weight and more reliable in dirty environments. The only benefits of pneumatics that I see are no return loop plumbing and less risk of oil contaminating product (still some risk as most pneumatic systems need oil). I would even consider generating electrical power off the PTO and using electric motors before considering pneumatic.

  • $\begingroup$ Thanks Eric. Yes, I am aware that Francis, Pelton and Kaplan are meant for incompressible fluids. Pneumatic or Turbochargers (as Dave had suggested) won't do because of numerous reasons - Torque, RPM, Dimensions, Fitment, etc. The turbine would be around 600-800 mm in dia. Possible to have a suitable runner? $\endgroup$
    – Ganesh
    Oct 20 '15 at 12:54

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